"Django Unchained" director Quentin Tarantino and its stars Leonardo DiCaprio and Jamie Foxx opened up about how difficult it was to work through the slavery film's dialogue and violent scenes in an exclusive interview with "Nightline."

"Django Unchained," which opened in theaters nationwide on Christmas Day, is a controversial film that defies classification. It is an epic revenge fantasy, romance and western. It is also surprisingly funny, a shock given the topic: slavery in the pre-Civil War American South, where slaves are shown being whipped and the n-word is used liberally.

"I don't think anybody is actually going out there saying that we used the word more excessively than it was used in 1858 in Mississippi," Tarantino said. "And if that's not the case, then they can shut up."

"A black person I was talking to says, 'Well, the n-word bothered me.' I said, 'It's supposed to,'" Foxx said. "Movies about the Holocaust happen every two or three or four years. When you think about slavery, we don't have any. This gives us an opportunity to open up the dialogue about that."

Foxx plays the title character Django, a freed slave on a blood-soaked mission to free his wife, Broomhilda, played by Kerry Washington. Foxx grew up in Texas and the horse he rides in the film belongs to him in real life.

The cowboy part felt natural, but to really inhabit the slave role, Tarantino told Foxx he would have to leave everything he had worked so hard for behind, meaning his identity as a Grammy-winning musician and the Oscar-winning star of "Ray," the 2004 biopic about the legendary Ray Charles.

"[Tarantino] looked at me and he says, 'But you got to be a slave,' and I went, 'What is that about?'" Foxx said. "And as I looked at my Louis bag and I looked at my Range Rover key, and he says, 'If you don't leave that outside, we're never going be able to tell a story. You have to be a person who can't read. You have to be a person who is trying to learn and follow his way,' which was tough for me because I've worked all my life to get to where I am as Jamie Foxx, and now he says, 'You're not there,' and so that's the other thing that you welcome. You welcome the challenge of Quentin Tarantino saying, 'If you do it the right way it'll be an iconic film.'"

"Django Unchained" is fast on its way to becoming one, with five Golden Globe nominations already and Oscar buzz swirling around all three men.

DiCaprio plays Calvin Candie, a slave owner and vicious racist who uses the n-word constantly. He said the first day reading lines on set with Foxx was "incredibly difficult" as he tried to say the n-word. Foxx and Samuel L. Jackson, who plays the house slave Stephen in "Django Unchained," stepped in to support their fellow actor.

"I said, 'What's the deal,'" Foxx said. "[DiCaprio] said, 'It's tough,' I said, 'You know what? You're human. It's supposed to be tough. You're not supposed to feel like its normal in 2012, 2013. Samuel Jackson quickly said, 'Hey, M.F., get over that. It's just another Tuesday for us and let's get going.'"

"We were all sitting around the table and they go, 'If you don't take this character to the utter extreme, if you don't speak the truth about the way we were treated at that time, people are going think this is sugar coated, that you're not telling the truth,'" DiCaprio added.

But after the initial discomfort, Foxx said DiCaprio embraced the part and worked hard to give an honest portrayal.

"I watched him and Sam go in their corners and they became these guys," Foxx said. "They didn't come out of it until the work was done."

"I don't think I could have embraced playing this character the way I did if I didn't have that support mechanism," DiCaprio said. "It felt like somebody was in my corner every single day saying, 'Push it further. Don't stop. Keep going with it. Keep going. Go to those extremes. Don't be afraid. No one here is going to get insulted.'"

It is an American story not often seen in Hollywood movies, but the reality of making a movie about slavery took its toll.

"It's one thing to write on the page, 'Cotton field in the background while two white characters are drinking lemonade, 100 slaves picking cotton in the background,'" Tarantino said. "It's another thing to plant that cotton and put 100 black folks in slave costumes broiling under the hot sun picking cotton. That can get to your soul a little bit."

So can watching a woman be whipped, as what happens to Washington's character, Broomhilda. Foxx and Tarantino agreed it was one of the toughest days on set and everyone from the catering staff to the director had tears in their eyes.

"I was shooting blind for a little bit because a tear got in the viewfinder and I couldn't see anything," Tarantino said. "But I just kept pointing where I thought that everything was."

"So at that moment, you felt the ancestors," Foxx said. "You felt the significance of why we're doing this film and showing it this way. That was something that happened every single day. So that was tough."

It goes without saying that Tarantino films are violent, and "Django Unchained" is no exception. It is loaded with violence, something the studio struggled with given the sensitivity to gun violence in the wake of the Sandy Hook Elementary School shooting in Newtown, Conn. But Tarantino made no apologies for his blood-soaked films and feels there is no connection between his work and violence in real life.

"In Shakespeare's time, he was blamed all the time for the anarchy in the streets. So there's violence in the streets. There's crime. Who do you blame? Blame the play makers, because it's very easy to blame them," he said. "The movies don't create a diseased mind. A diseased mind has a zillion triggers, and it's not just cinema."

"Let's mourn these victims. Let's give them that respect," Foxx added. "Unfortunately you can't look to a film director or actors and say, 'If you stop doing what you're doing, that guy over there is not going to go do something.'"